The present invention relates to a disk brake for use in a vehicle, for example, an automobile, to apply braking force thereto.
In general, a disk brake used in a vehicle, e.g. an automobile, has a caliper body extending over the outer periphery of and in the axial direction of a disk that rotates together with a wheel of the vehicle, a piston projectable from the caliper body in the axial direction of the disk and having an annular contact part at an end thereof at which the piston is projectable, and a friction pad that is pressed against the disk by the piston (for example, see Japanese Patent Application Publication No, Hei 10-122277).
When the driver of the vehicle, for example, operates the brake, the piston is slidingly displaced toward the disk by a hydraulic pressure supplied externally, for example. Thus, the piston presses the friction pad toward the disk, thereby applying braking force to the disk.
Incidentally, the load (surface pressure) applied to the disk from the friction pad during braking is likely to become larger at the entrance side in the rotational direction of the disk (i.e. rotational entrance side) than at the exit side in the rotational direction of the disk (i.e. rotational exit side). In the disk brake of Japanese Patent Application Publication No. Hei 10-122277, a shim plate formed from a metal plate or the like is provided between the rear side of the friction pad and the piston. The shim plate is provided with an elongated cut portion in a region that is abutted by the annular contact part of the piston to adjust, by the cut portion, the surface pressure of the friction pad applied to the disk.
More specifically, the cut portion is provided in the shim plate at a position on the rotational entrance side in the direction of rotation of the disk when the vehicle travels forward to reduce the load at the position where the cut portion is provided. With this structure, the load from the annular contact part of the piston can be transmitted to the friction pad through the shim plate such that a reduced load is applied to the rotational entrance side of the friction pad. Accordingly, it is possible to suppress uneven wear of the friction pad (lining thereof) and occurrence of brake noise or judder.
However, when the external size (diameter) of the piston (annular contact part) is smaller than the diametrical length and circumferential length of the shim plate, for example, if an elongated cut portion is merely provided in the shim plate, the piston may tilt about the peripheral edge of the cut portion serving as a fulcrum.
In such a case, the load from the piston concentrates on a portion of the shim plate that serves as a fulcrum of tilting, so that the load applied to the friction pad from the piston may become non-uniform. Consequently, the friction pad is likely to wear unevenly, and judder may occur with time.
The present invention has been made in view of the above-described problems with the related art. Accordingly, an object of the present invention is to provide a disk brake capable of reducing brake noise, uneven wear or the friction pad, occurrence of judder, and so forth to improve performance.